rotork Pakscan IIS, Техническое руководство

Страница: 25 / 84

Pakscan IIS Technical Manual Issue 1.0
Publication S130E 25
If there is no signal earth bar
- one of the two links LK4 or LK5
should be fitted. Connect the screen to the master station on both
ends of the cable and fit either LK4 or LK5.
If there is a signal earth bar - one of the screens may be connected
to the bar in addition to them both connecting to the master station,
in this configuration both LK4 and LK5 should be removed.
7.4 Loop Checks
Once the loop is fully wired there are a number of checks that should be made before power is applied to any
of the connected field units, actuators, or the master station. These simple tests will always help in the setting to
work of the system.
a) Loop Continuity.
With all the field units connected, but none of them powered up, check the continuity of the 2 cores of the
cable using a simple ohm meter. [The most common errors in installing the system occur on the field wiring.]
To do this disconnect all the loop wires and the screen from the master station.
Measure, and note down, the resistance of each core (they should both be the same as the cable is a pair).
Check the resistance between the cores, this should be a high resistance as they are not connected together.
(Note that if a field unit has power to it, then the internal circuitry will connect the two cores together.)
Join the 2 wires that will be connected to Port B together and measure the total resistance of the whole loop
cable - note this down as you will need it for reference later.
b) Screen Continuity
With the Port B cables still connected together make sure that the screen is isolated from the loop cores
themselves, there should be a high resistance between screen and cores.
Now check that the screen is isolated from earth by measuring the resistance between the screen and your
screen earth point.
20
21
22
Port B IN
Port B OUT
SAFETY EARTH
17
18
19
Port A OUT
Port A IN
Cable A
Cable B
LK4
LK5
20
21
22
Port B IN
Port B OUT
SAFETY EARTH
17
18
19
Port A OUT
Port A IN
Cable A
Cable B
LK4
LK5
Earth Bar
Fig. 12: Screen connection